USB 3.0 Speed
Both Fusion 8 and Parallels 11 support USB 3.0 devices with USB 3.0-compatible host hardware. In theory, this lets the user access their flash drives and external USB hard drives directly from within the VM without a significant loss in speed. But the VM still has to translate the USB 3.0 signal from the host hardware to its own virtual hardware, and there are likely to be performance compromises in that process.
To test just how well our virtual machines could handle USB 3.0 transfers, we used a 1TB Samsung 850 Pro SSD and connected it to our test setup via the StarTech USB 3.1 Single-Bay Dock (our MacBook Pro does not have USB 3.1 support, but the dock is fully backwards-compatible with USB 3.0 devices). With a theoretical bandwidth limit of 5Gbps (and a real-world limit even lower), no USB 3.0 interface can accommodate the full speed of our Samsung SSD. Therefore, this isn’t a test of the maximum speed of the SSD itself, but rather a comparative test of how fast each virtual machine can perform sequential read and write operations.
We used ATTO Disk Benchmark to measure transfer speed in megabytes per second at transfer sizes between 512 bytes and 64 megabytes. A higher number on the y-axis indicates faster speed. To give us a baseline result, we also tested this setup natively via Boot Camp. First up is read performance:
Natively via Boot Camp, we achieved maximum USB 3.0 speeds of about 460MB/s. Of our virtualization platforms, Fusion 8 clearly wins on USB 3.0 reads, coming in not far behind Boot Camp with max speeds of about 425MB/s. VirtualBox surprisingly holds its own in this race, offering similar performance to Parallels 11, albeit with a performance drop-off at the largest transfer sizes.
USB 3.0 write performance is a little more complicated. Boot Camp gives us a performance baseline of around 420MB/s, and Fusion 8 achieves the best speed at large transfer sizes of about 350MB/s, but both Parallels 11 and VirtualBox offer faster speeds at small transfer sizes, with the tipping point right around 2MB/s. Therefore, if you need your VM to transfer lots of small files like text documents and spreadsheets to an external USB 3.0 device, you may see better performance with Parallels (or VirtualBox), but for large files like movies and games, Fusion 8 will be your better option.